\section{Experimental Results}
\label{sec:results}

The Over-Subscription Planner was integrated with T-REX and tested in
simulation as well as at sea in the course of a series of sea trials in
the Monterey Bay, California. Figure 5 gives an example of the scenarios
used to test the algorithm. Nodes define positions of interest in
latitude and longitude. Links are directed edges between node pairs. The
horizontal and vertical scales of the test area are approximately 0.006
decimal degrees longitude and latitude respectively. 4 goals are
shown. The science goals were to conduct a path survey from a start node
to an end node. A path survey enables the AUV to travel the shortest
path between these nodes within a depth range while running a range of
science instruments. The mission also includes an operator goal to have
the vehicle ready for pickup at the designated node. The subscript
attached to each goal indicates its priority. Throughout mission
execution, the vehicle is subject to an operations constraint on the
length of time the vehicle may remain submerged after which it must
pre-empt its work and surface to localize using GPS. The duration of
this task depends on the conditions at the surface. With high sea state,
the wave action can inhibit the GPS. The vehicle will wait at the
surface until it obtains the desired number of GPS hits. The mission is
subject to a maximum duration constraint.

We have 2 key mechanisms to adjust the problem. By reducing the mission
duration we can make the problem over-subscribed. By forcing the vehicle
to linger when localizing we can simulate a case where unforeseen
execution delays cause the plan to break. Using these methods, we have
successfully demonstrated a number of cases that were over and under
subscribed during execution. For example, given the goal set in Figure
5, we constrained the mission to terminate in 1000 seconds, and localize
every 240 seconds with a delay at the surface of 150 seconds. The
initial position was close to F. The initial plan correctly dropped the
survey goal along EA, but included all other goals. The planned path was
DCBF.  The delay accrued at the surface resulted in a projected failure
during the traverse DC. Dropping the goal to survey along BF repaired
the plan. The final path was DCF.
